The problems connected with measuring the surface temperature of high temperature bodies, for example in the temperature range of from 500.degree. C. to 2000.degree. C., have mostly been solved by well known pyrometric techniques, and in particular by optical pyrometry.
When temperatures are measured under favorable conditions, for example when on the optical path used for the measurement no disturbance whatsoever is found, the results of the said measurements actually correspond to the qualities to be measured.
However, this is not the case when measurements are to be made in an environment the atmosphere of which comprises disturbing components possibly in variable amounts such as powders of any kind, vapors (for example steam), and various mists. The presence of such components on the path of the pyrometric optical measurement necessarily leads to alterations which affect to a greater or lesser extent the accuracy of the results obtained and also prevent them from being reproducible.
When one finds oneself in similar conditions, the remedy is obviously to eliminate as far as possible in any measurement these disturbing components and to suppress the causes governing their production.
Frequently, however, temperatures have to be measured in places where the production or the passage of disturbing components, such as powders and coolant projections, and the presence of an oxide layer, are fundamental aspects of the phenomenon in question, or are even the conditions for this phenomenon taking place correctly. In this case, it is not possible to eliminate the disturbance elements without modifying the process taking place; the problem of measuring the temperature is then solved in an unsatisfactory manner.
To the knowledge of the applicants, there is not in existence up to now a valuable method for measuring the real temperature under difficult operational conditions such as those mentioned above.